This invention relates to oscilloscopes and, more particularly, to a video synthesizer for combining and sampling a set of input signals to generate a continuous flicker-free presentaton on the oscilloscope of a complete set of the signals.
Oscilloscopes are widely used in the laboratory for examination of electronic signals. Frequently, it is advantageous to simultaneously view a plurality of signals. To meet this need, oscilloscopes have been constructed with two input channels wherein each input channel is to be utilized in viewing a separate input signal. One mode of construction of a dual channel oscilloscope is known as a dual-beam oscilloscope wherein two separate electron beams are directed towards the face of the oscilloscope with the aid of separate beam-deflection circuitry. A second mode of construction of a dual channel oscilloscope is known as a dual-trace oscilloscope wherein the input circuitry for a single electron beam is made to switch alternately between two input terminals of the oscilloscope. With both forms of construction, the dual channel oscilloscope is capable of presenting pictorial representations of electronic signals concurrently on the face of the oscilloscope. With the dual-beam oscilloscope, the two input signals are continuously displayed, one signal being displayed by each of the two beams. With the dual-trace oscilloscope, the pictorial representation is actually a set of alternating sampling intervals of the two signals; however, the rate of alternation between the two sampling intervals is sufficiently high to be above the flicker rate so as to present a flicker-free presentation of the two signals on the face of the oscilloscope.
A problem arises in that there are many situations, particularly in the examination of digital electronic circuits, when it is essential to examine simultaneously the waveforms of many more than just the two signals described above with reference to the dual channel oscilloscope. Obviously, one solution to the problem is to utilize more than one dual-channel oscilloscope. However, this clearly becomes unwieldy and impractical, both in terms of cost and in terms of the space required in the laboratory. Also, the use of separate displays does not permit visual alignment of the various portions of the waveforms of the electronic signals. Ideally, it would be desirable to be able to view many digital waveforms simultaneously on the face of the oscilloscope. However, the foregoing dual-channel oscilloscopes are limited to the display of only two signal waveforms at the same time.